The Meaning of the Donovan Index is simple. The scores reflect the rate at which cities' teams, and thus cities themselves, win major professional sports championships. If you want to see the math behind the scores, click Formula.
The Results of the index do not therefore reveal the "best" sports cities, although they certainly factor into any such ranking. The "best" sports cities combine tradition, passion, and success on the field. Philadelphia and St. Louis are great sports cities even if their teams do not win championships at an average rate. Los Angeles is a true city of champions, but many consider it a front-running town indifferent to anything less than a first-place contender. Of course, there are towns like New York and Boston that have it all: tradition, passion, and championships. These are ultimately the "best" sports towns. By contrast, there are towns with a history of losing and disinterest - Atlanta comes to mind.
So Enjoy the Index. Use it to settle arguments at bars and game-watching parties, or maybe to start arguments. Just remember what it is and what it is not...and let the trash talking begin.